fix: Add missing @classmethod decorators to field validators

- Add @classmethod decorator to validate_file_path in base_file_knowledge_source.py
- Add @classmethod decorator to validate_file_path in excel_knowledge_source.py
- Follows existing codebase pattern for Pydantic field validators (N805)

Co-Authored-By: João <joao@crewai.com>

src/crewai/knowledge/source/base_file_knowledge_source.py

@@ -1,12 +1,10 @@
 from abc import ABC, abstractmethod
 from pathlib import Path
-from typing import Dict, List, Optional, Union
 
 from pydantic import Field, field_validator
 
 from crewai.knowledge.source.base_knowledge_source import BaseKnowledgeSource
 from crewai.knowledge.storage.knowledge_storage import KnowledgeStorage
-from crewai.utilities.constants import KNOWLEDGE_DIRECTORY
 from crewai.utilities.logger import Logger
 from crewai.utilities.paths import get_knowledge_directory
 
@@ -15,18 +13,19 @@ class BaseFileKnowledgeSource(BaseKnowledgeSource, ABC):
     """Base class for knowledge sources that load content from files."""
 
     _logger: Logger = Logger(verbose=True)
-    file_path: Optional[Union[Path, List[Path], str, List[str]]] = Field(
+    file_path: Path | list[Path] | str | list[str] | None = Field(
         default=None,
         description="[Deprecated] The path to the file. Use file_paths instead.",
     )
-    file_paths: Optional[Union[Path, List[Path], str, List[str]]] = Field(
+    file_paths: Path | list[Path] | str | list[str] | None = Field(
         default_factory=list, description="The path to the file"
     )
-    content: Dict[Path, str] = Field(init=False, default_factory=dict)
-    storage: Optional[KnowledgeStorage] = Field(default=None)
-    safe_file_paths: List[Path] = Field(default_factory=list)
+    content: dict[Path, str] = Field(init=False, default_factory=dict)
+    storage: KnowledgeStorage | None = Field(default=None)
+    safe_file_paths: list[Path] = Field(default_factory=list)
 
     @field_validator("file_path", "file_paths", mode="before")
+    @classmethod
     def validate_file_path(cls, v, info):
         """Validate that at least one of file_path or file_paths is provided."""
         # Single check if both are None, O(1) instead of nested conditions
@@ -47,9 +46,8 @@ class BaseFileKnowledgeSource(BaseKnowledgeSource, ABC):
         self.content = self.load_content()
 
     @abstractmethod
-    def load_content(self) -> Dict[Path, str]:
+    def load_content(self) -> dict[Path, str]:
         """Load and preprocess file content. Should be overridden by subclasses. Assume that the file path is relative to the project root in the knowledge directory."""
-        pass
 
     def validate_content(self):
         """Validate the paths."""
@@ -75,11 +73,11 @@ class BaseFileKnowledgeSource(BaseKnowledgeSource, ABC):
         else:
             raise ValueError("No storage found to save documents.")
 
-    def convert_to_path(self, path: Union[Path, str]) -> Path:
+    def convert_to_path(self, path: Path | str) -> Path:
         """Convert a path to a Path object."""
         return Path(get_knowledge_directory() + "/" + path) if isinstance(path, str) else path
 
-    def _process_file_paths(self) -> List[Path]:
+    def _process_file_paths(self) -> list[Path]:
         """Convert file_path to a list of Path objects."""
 
         if hasattr(self, "file_path") and self.file_path is not None:
@@ -94,7 +92,7 @@ class BaseFileKnowledgeSource(BaseKnowledgeSource, ABC):
             raise ValueError("Your source must be provided with a file_paths: []")
 
         # Convert single path to list
-        path_list: List[Union[Path, str]] = (
+        path_list: list[Path | str] = (
             [self.file_paths]
             if isinstance(self.file_paths, (str, Path))
             else list(self.file_paths)

src/crewai/knowledge/source/excel_knowledge_source.py

@@ -26,6 +26,7 @@ class ExcelKnowledgeSource(BaseKnowledgeSource):
     safe_file_paths: list[Path] = Field(default_factory=list)
 
     @field_validator("file_path", "file_paths", mode="before")
+    @classmethod
     def validate_file_path(cls, v, info):
         """Validate that at least one of file_path or file_paths is provided."""
         # Single check if both are None, O(1) instead of nested conditions